Climate and Average Weather Year Round at Lewiston–Nez Perce County Airport Idaho, United States

At Lewiston–Nez Perce County Airport, the summers are short, hot, dry, and mostly clear and the winters are very cold and partly cloudy. Over the course of the year, the temperature typically varies from 30°F to 93°F and is rarely below 18°F or above 102°F.

Based on the tourism score, the best time of year to visit Lewiston–Nez Perce County Airport for warm-weather activities is from early July to late August.

The hot season lasts for 2.6 months, from June 21 to September 9, with an average daily high temperature above 82°F. The hottest month of the year at Lewiston–Nez Perce County Airport is July, with an average high of 91°F and low of 62°F.

The cold season lasts for 3.4 months, from November 11 to February 23, with an average daily high temperature below 50°F. The coldest month of the year at Lewiston–Nez Perce County Airport is December, with an average low of 31°F and high of 41°F.

At Lewiston–Nez Perce County Airport, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year at Lewiston–Nez Perce County Airport begins around June 14 and lasts for 3.8 months, ending around October 7.

The clearest month of the year at Lewiston–Nez Perce County Airport is July, during which on average the sky is clear, mostly clear, or partly cloudy 77% of the time.

The cloudier part of the year begins around October 7 and lasts for 8.2 months, ending around June 14.

The cloudiest month of the year at Lewiston–Nez Perce County Airport is January, during which on average the sky is overcast or mostly cloudy 64% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Lewiston–Nez Perce County Airport varies throughout the year.

The wetter season lasts 8.0 months, from October 20 to June 19, with a greater than 23% chance of a given day being a wet day. The month with the most wet days at Lewiston–Nez Perce County Airport is November, with an average of 10.5 days with at least 0.04 inches of precipitation.

The drier season lasts 4.0 months, from June 19 to October 20. The month with the fewest wet days at Lewiston–Nez Perce County Airport is August, with an average of 2.7 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone at Lewiston–Nez Perce County Airport is November, with an average of 9.9 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 35% on November 18.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Lewiston–Nez Perce County Airport experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year at Lewiston–Nez Perce County Airport. The month with the most rain at Lewiston–Nez Perce County Airport is November, with an average rainfall of 2.2 inches.

The month with the least rain at Lewiston–Nez Perce County Airport is August, with an average rainfall of 0.5 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Lewiston–Nez Perce County Airport experiences some seasonal variation in monthly snowfall.

The snowy period of the year lasts for 2.3 months, from November 30 to February 8, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow at Lewiston–Nez Perce County Airport is December, with an average snowfall of 2.0 inches.

The snowless period of the year lasts for 9.7 months, from February 8 to November 30. The least snow falls around July 14, with an average total accumulation of 0.0 inches.

The length of the day at Lewiston–Nez Perce County Airport varies significantly over the course of the year. In 2024, the shortest day is December 21, with 8 hours, 35 minutes of daylight; the longest day is June 20, with 15 hours, 48 minutes of daylight.

The earliest sunrise is at 4:55 AM on June 15, and the latest sunrise is 2 hours, 37 minutes later at 7:31 AM on November 2. The earliest sunset is at 4:01 PM on December 10, and the latest sunset is 4 hours, 43 minutes later at 8:44 PM on June 25.

Daylight saving time (DST) is observed at Lewiston–Nez Perce County Airport during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level at Lewiston–Nez Perce County Airport, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at Lewiston–Nez Perce County Airport experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.1 months, from October 22 to May 26, with average wind speeds of more than 6.4 miles per hour. The windiest month of the year at Lewiston–Nez Perce County Airport is March, with an average hourly wind speed of 7.0 miles per hour.

The calmer time of year lasts for 4.9 months, from May 26 to October 22. The calmest month of the year at Lewiston–Nez Perce County Airport is August, with an average hourly wind speed of 5.7 miles per hour.

The predominant average hourly wind direction at Lewiston–Nez Perce County Airport varies throughout the year.

The wind is most often from the west for 7.7 months, from March 4 to October 26, with a peak percentage of 57% on June 20. The wind is most often from the south for 4.3 months, from October 26 to March 4, with a peak percentage of 53% on January 1.

To characterize how pleasant the weather is at Lewiston–Nez Perce County Airport throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Lewiston–Nez Perce County Airport for general outdoor tourist activities is from early July to late August, with a peak score in the first week of August.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Lewiston–Nez Perce County Airport for hot-weather activities is from mid July to mid August, with a peak score in the last week of July.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at Lewiston–Nez Perce County Airport typically lasts for 7.2 months (221 days), from around March 25 to around November 2, rarely starting before February 28 or after April 18, and rarely ending before October 11 or after November 24.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms at Lewiston–Nez Perce County Airport should appear around April 6, only rarely appearing before March 24 or after April 21.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.1 months, from May 19 to August 21, with an average daily incident shortwave energy per square meter above 6.4 kWh. The brightest month of the year at Lewiston–Nez Perce County Airport is July, with an average of 7.5 kWh.

The darker period of the year lasts for 3.7 months, from October 26 to February 18, with an average daily incident shortwave energy per square meter below 2.5 kWh. The darkest month of the year at Lewiston–Nez Perce County Airport is December, with an average of 1.3 kWh.

For the purposes of this report, the geographical coordinates of Lewiston–Nez Perce County Airport are 46.374 deg latitude, -117.015 deg longitude, and 1,434 ft elevation.

The topography within 2 miles of Lewiston–Nez Perce County Airport contains significant variations in elevation, with a maximum elevation change of 778 feet and an average elevation above sea level of 1,213 feet. Within 10 miles contains significant variations in elevation (2,365 feet). Within 50 miles contains large variations in elevation (5,741 feet).

The area within 2 miles of Lewiston–Nez Perce County Airport is covered by grassland (31%), artificial surfaces (30%), and shrubs (28%), within 10 miles by grassland (38%) and cropland (36%), and within 50 miles by shrubs (33%) and cropland (32%).